Snap-acting mechanism



Dec. 25, 1962 J. P. WATSON 3,069,916

SNAP-ACTING MECHANISM Filed Jan. 11, 1960 2 Sheets-Sheet l JAMES WATSON,

INVENTOR.

HERZIIG & JESSUP Dec. 1962 J. P. WATSON 3,069,916

SNAP-ACTING MECHANISM Filed Jan. 11, 1960 2 Sheets-Sheet 2 JAMES P.WATSON,

INVENTOR. 92

HERZIG 8: JESSUP,

Attorneys Q/QMMTW United States Patent Office 3,069,916 Patented Dec.25, 1962 3,069,916 SNAP-ACTHNG MECHANESM James P. Watson, Miami Shores,Fla, assignor of one half to Joe Davidson, South Gate, Calif. Filed Jan.11, 13360, Ser. No. 1,539 6 Claims. (Ci. 74--1tiil) This inventionrelates to snap-acting mechanisms, for example snap-acting electricswitches.

It is an object of this invention to provide a snap-acting mechanismconsisting of a bowed leafspring member which is unbroken throughout itslength, being of uniform cross-section throughout its entire length.

It is another object of this invention to provide in a snap-acting leafspring mechanism, a combined return spring and shunt, which is formedintegral with the leaf spring, both of the integral parts, viz. leafspring and return spring, being of uniform cross-section throughout theentire length of the integral members.

It is another object of this invention to provide improved means foractuating a bowed, snap-acting leaf spring from one stressed position tothe other.

It is a further object of this invention to provide a snapactingmechanism operated by a reciprocable push button, which may be adjustedin easy manner to provide an adjustable stroke of the push button,between operated positions of the snap-acting member or leaf spring.

it is a further object of this invention to provide an improved jointbetween two portions of the housing or case of an electrical equipmentsuch as an electrical switch.

It is another object of this invention to provide an improvedsnap-acting leaf spring, wherein the pivot shafts at one or both ends ofthe spring are formed integral with the leaf spring itself.

It is a further object of this invention to provide simple and effectivemeans to control and adjust the limit stops of a push button foroperating a snap acting leaf spring.

In accordance with these and other objects which will become apparenthereinafter, preferred forms of the present invention will now bedescribed in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view, broken away and partially sectioned,illustrating one form of snap-acting mechanism constructed in accordancewith the present invention.

FIG. 2 is a fragmentary sectional elevation illustrating the operatingend of the snap-acting mechanism.

FIG. 3 is a fragmentary plan view of the push button actuating mechanismfor the snap-acting mechanism.

FIG. 4 is a sectioned perspective view of another form of the presentinvention.

FIG. 5 is a cross-section taken on line 5 in FIG. 4.

Referring to FIG. 1, 11 designates a case or housing, preferably made ofinsulating material. The housing is made in two parts separated at aparting surface or plane 12 offset at 13 and continued at 14.

Held within the housing 11 is a conducting frame 16 having upstandingportions 1'! at each end thereof, from which project pairs of shelves18. The spaces 1% between the shelves 18 form bearings for pivot shaftmeans formed at each end of a bowed resilient leaf spring 21. At eachend, the leaf spring 21 is bent back on itself in the shape of a loop 22to form a shaft means journaled in the space The total length of theleaf spring 21, including the shaft loops 22, is slightly greater thanthe distance between the bearing portions 19, and as a consequence theresilient spring 21 is compressed and bowed between the two arms 17 ofthe frame 16.

In FIG. 1 the right hand end of the leaf spring 21 constitutes theoperating end. The shaft loop 22, after being bent back upon the mainportion of the leaf spring 21 and welded at 23, is returned underneaththe leaf spring 21 to form a serpentine return spring and shunt 24. Theshunt 24 has two reverse bends as shown, the end being secured againstthe body of the frame 16 underneath an insulating ledge 26. The leafspring 21 and shunt 24 are made of a single strip of resilient metal ofuniform cross-section throughout its length, and is unbroken as shown.The portion 24 serves as a return spring which keeps the leaf springportion 21 biased to its upwardly bowed position, from which it issnapped to its lower bowed position by a push button means or member nowto be described.

Joined to the operating shaft loop, as by spotwelding 27, is a tab orplate 28 made of metal, which is thick enough to be substantially rigidcompared to the flexibility of the leaf spring 21, which is relativelythin. The tab 28 constitutes an operating member for snapping the leafspring 21 to its downward position. It extends away from the axis of theshaft loop 22 generally parallel to and overlying the surface of theleaf spring 21. Reciprocably mounted in a bore 29 in the upper portionof the case 11 is a push button 31. On the lower end of the push button31 is a disk 32, from the lower portion of which extends a roundedprotuberance or button 33, that engages the operating tab 28 to snap theleaf spring 21 to its downward position. The protuberance 33 is locatedappreciably from the axis 34 of the shaft loop 22, and thereforepressure upon the push button 31 causes a torque to be applied to theshaft loop 22, which serves to snap the leaf spring 21 to its downwardbowed position. When pressure is released from the push button 11, theresilient bias of the serpentine leaf spring portion 24, also actingthrough the shaft loop 22, snaps the leaf spring 21 back to its upperposition, shown in FIG. 1.

The distance which the push button 31 is required to travel in order tosnap the leaf spring 21 to its downward bowed position is dependent uponthe distance from the axis 34 to the point of engagement between theprotuberance or button 33 and the operating tab 28. This latter distancemay be adjusted by rotating the push button 31 about its axis. This iseffected by reciprocably mounting the push button 31 in a grommet 36,which may be rotated within the bore 29 of the housing 11. To simplifyrotation of the push button 31, it is made hexagonal, so that its outerfaces 38 may be engaged by a wrench or other suitable tool andappropriately rotated.

To indicate externally the position of the operating button 33, thegrommet 36 is provided with an apron 39 aving indicia 41 located aroundits edge, which cooperate with an index mark 4-2 on the case 11. Thepush button 31 is keyed to the grommet 36 by a groove 43 cooperatingwith an engaging an inwardly extending spline 44 on the grommet 36.

One of the advantages of the present structure is that the length of thecase 11 is held to a minimum by placing the two pivot shafts 22 atvirtually the end extremities within the case 111. This is achieved byoperating the leaf spring 21 from within the region bounded by the shaftloops 22, i.e., bounded by two parallel planes substantially normal tothe leaf spring 21 and located at the respective ends of the leaf spring'21, i.e., at the shaft loops 22. This advantage is attained while stillretaining the full functional operating length of the resilient leaf 21,by providing the relatively rigid operating tab 28 joined to the pivotshaft portion 22 and extending back over the leaf 21 itself.

It is desirable to provide stops for limiting both the upward anddownward excursions of the push button 31. To that end the case 11 isprovided with an inwardly extending stop in the form of a shelf 46located above the disk 32, and with a second inwardly extending stop inthe form of another shelf 47 located below the disk 32, i.e., betweenthe disk 32 and the operating tab 28.

Shelf 46 forms an upper stop limiting the upward or unoperated travel ofthe push button 31 and shelf 4-7 forms a lower stop limiting thedownward or operated travel of the push button 31. The lower shelf 47 isparticularly important in that it prevents the push button 31 from beingpushed downward an excessive amount after it has already eifectuateddownward snapping of the leaf spring 21. Such excessive downward travelon the part of the push button 31 might cause damage to the leaf spring21 or might bend the tab 28, thereby disturbing the geometricrelationship between the tab 28 and the leaf spring 21, which in manyuses could be quite critical.

As noted, the push button 31 is rotatable to adjust the amount of travelrequired to cause the leaf spring 21 to snap to its downward position.When the push button is rotated so as to bring the operatingprotuberance or butt-on S3 to its farthest left position, the pushbutton 31 must be depressed a maximum in order to snap the leaf spring21. Conversely, when the rotational adjustment of the push button 31 issuch as to bring the protuberance 33 to its fanthest right position,then the travel required of the push button 31 is a minimum.

In accordance with the present invention the down stop position of thepush button 31 is appropriately and automatically adjusted to compensatefor the travel necessary to snap the leaf spring 21 over. This iseffected by forming the annular undersurfaee of the disk 32 on anoblique angle with respect to a plane normal to the axis of the pushbutton 31. Thus, as shown in FIG. 2, when the button 33 is farthest tothe left, the thinnest portion of the disk 32 resides above the stopshelf 47, thus allowing maximum travel of the push button 31.Conversely, when the button 33 is farthest to the right the thickestportion of the disk 32 resides over the stop shelf 47 and allows minimumtravel of the push button 31 before it engages its downward stop.

This design lends itself elegantly to adjustment and selection ofparameters which provide a wide range of adjustability in the operatinglimits of the push button 31. Referring to FIG. 2, the reference line 51is a horizontal reference line denoting simply Zero angle of deviationfrom the horizontal. Reference line 52 is a reference line parallelingthe undersurface 53 of the disk 32. Thus the angle 54 represents theobliquity of undersurface 53 from the horizontal. Similarly thereference line 56 is an angular line of reference paralleling the uppersurface 57 of the disk 32. Thus, the angle 58 represents the obliquityof the surface 57 with respect to the horizontal. in the specific formshown in FIG. 2 angle is zero, while angle 54 is about 5.

Also in FIG. 2, the line 61 represents the height of the top surface 62of the push button 31 when it is upward, in its unoperated position,with the stop disk 32 bearing against the stop shelf 4s. The distance 63represents the height of this surface 62 above an arbitrary horizontalreference surface, chosen in this case as the upper surface of the caseill. The line 64 represents the level of the surface 62 when the stopdisk 32 bears against the lowermost stop shelf 47. The distance 66represents the height of the surface 62 above the arbitrary referencesurface, for this condition of operation. This distance as is onlyslightly less than the position of the reference line as at the momentwhen the leaf 21 snaps downward to its lower bowed position. That is tosay, the parameters and dimensions are so adjusted that the stops 32 andt? come into engagement very shortly after the leaf spring has snappedover. Similarly as pressure on the push button 31 is released, the steps32 and 46 come into engagement very shortly after the leaf spring 21 hasbeen returned to its upper bowed position by the bias of the serpentinereturn spring 2t.

Reference line 71 is an angular reference line paralleling the uppersurface 72 for the operating tab 28 in the unoperated position of thepush button 31, i.e., when the leaf spring 21 is in its upper bowedposition. Reference line 73 is .1 angular reference line paralleling thesurface 72 when the push button 31 is in its lower position with thestops 32 and 47 in engagement. Thus angle represents the obliquitybetween the surface 72 and a horizontal reference plane 51 in theunoperated position of the push button 31; and angle 76 represents theobliquity between the surface 72 and the arbitrary hori- Zontalreference surface 51 when the push button 31 is in its lowermostposition.

When the switch is designed so that angle 74 is zero, dimension 63 willbe constant for all notative positions of the push button 31, i.e., allpositions of the operating button 33 with respect to the axis 34. Anychanges in stroke length brought about by angular adjustment of the pushbutton 31 are reflected in corresponding changes in dimension 66, i.e.,the operated position of the push button 31. When angle 74 is Zero,angle 58 is made zero, since the uppermost position of the surface 62 isconstant for all rotative positions of the push button 31. Under thiscondition angle 54 is a maximum to compensate appropriately for allrotative positions of the push button 31.

At the other extreme, let it be assumed that the tab 28 is bent upwardfar enough, for example, to bring the angle 7a: to zero. That is to say,the tab 28 is bent up a sumcient extent so that when the push button 31is depressed, the leaf spring 21 snaps to its downward position just asthe surface 72 comes horizontal. For this adjustment of the tab 28, theangle 54 on the disk 32 would be made zero, and the angle 58 of theupper surface 57 would be made a maximum. The net result of thesechanges in parameters would be that the dimension 66 would remainconstant for all angular adjustments of the push button 31, and suchangular adjustments would cause a progressive change in the dimension63. From the above it will be clear that any desired adjustment of theinitial setting of the tab 28 may be made, with a corresponding andcorrelated change in the surfaces 57 and 53, and a consequent controlover the dimensions 66 and 63, as desired.

The snap acting mechanism has been illustrated in FIG. 1 as a doublethrow single pole electric switch, wherein the leaf spring 21 carries apair of contacts 81 on opposite sides of the leaf. These contacts comeinto engagement respectively with stationary contacts 82 and 83 whichare connected with respective external terminals 84 and 86.

The serpentine resilient member 24, in addition to erving as a returnspring for the leaf member 21, also serves as a shunt carrying currentdirectly and without sliding contact from the leaf 21 to the frame 16and then to the terminal 87. To this end the lower end of the returnspring 24 is bonded to the frame 16 at 88 and lies under theaforementioned insulating ledge 26 which projects from the far wall 91of the case 11.

For ease of construction, stationary contact 83 extends the full widthof, and is formed integral with, the terminal 85. It is overlaid with aprecious metal covering 92 at the particular region where it is engagedby the movable contact 81.

The two halves 91 and 93 of the case 11 are held together by a toughplastic band 94 seated in a groove 96 formed around the case ill.

For external mounting of the switch mechanism, a solid portion 97 isformed within the interior of the housing 11 and through it passes abore 98, by means of which the mechanism may be suitably mounted oranchored, without endangering the sealed nature of the interior of thecasing llll.

Another configuration of the switch means is shown in FIGS. 4 and 5. Inthis embodiment the housing 11' is made cylindrical instead ofrectangular, and the push button 31 operates on an axis substantiallyparallel to the length of the leaf spring 21. To link push button 31' tothe leaf spring 21', the shaft 22', instead of being formed by theshaping of the leaf spring itself, is made of a solid member (journaledin the recess 19') to which is integrally formed a semicircular yoke28', which extends substantially at right angles to the surface of theleaf spring member 21'. Engaging the yoke 28' is a protuberance orbutton 33 formed on the end of the reciprocable push button 31. As inFIG. 1, the push button 31 is rotatable about its axis to cause thebutton 33' to hear at adjustable points on the yoke 28, which are atvarying radii from the axis of the shaft 22'. In this way the stroke ofthe push button 31: may be adjusted in a manner generally similar tothat of the push button 31 of FIGS. 1 and 2.

In the embodiment shown in FIG. 4, the shaft 22. is provided with a slot101, within which the leaf spring 21 is folded directly back on itself,emerging from the slot 1G1 to form the serpentine return spring 24. Itwill be noted that the convolutions of the spring 24' extend generallyparallel to the leaf spring 21, whereas in FIG. 1 the convolutionsextended generally downward at right angles away from the surface of theleaf spring 21. However, the function of the serpentine leaf springs 24and 24 is substantially similar, namely to apply a constant return biastorque to the shaft 22, to snap the leaf 21' to its downward position,whenever pressure is released from the push button 31'.

In the embodiment shown in FIG. 4, the cylindrical case 11 is formed oftwo substantially semi-cylindrical portions 91 and 92, which are joinedtogether by a stepjoint shown at 196. In this joint the surfaces 107 and1nd are made substantially flush with each other, whereas a gap betweenadjacent surfaces is deliberately left at 139. In the assembly of thehousing or case 11, cement is cotated the lower of the surfaces whichare to form the gap 109, and then the two halves are brought together,with the surfaces 108 sliding tightly against each other, until thesurfaces 107 bottom. This leaves the gap 109 filled with compressedcement to bond the two halves together. By virtue of this constructionthe casing halves are precisely positioned relative to each other, thethickness of cement in the joint is exactly as desired, and entrance ofcement into the casing is prevented.

All terminals exit through the end wall, as shown in FIG. 5.

An annular mounting flange 112 encircling the housing 11' is providedfor mounting the switch mechanism to any suitable chassis or base.

While the instant invention has been shown and de scribed herein in whatis conceived to be the most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of theinvention which is therefore not to be limited to the details disclosedherein but it to be afforded the full scope of the claims.

What is claimed is:

l. Snap-acting mechanism comprising frame means having pivot bearingmeans at each end, resilient leaf spring means compressed and bowedbetween said pivot bearing means, and being of uniform, unbrokencrosssection between said bearing means, one end of said leaf springmeans being an operating end, shaft means at said operating endjournalled in the adjacent corresponding pivot bearing means, saidoperating end of said leaf spring means being joined to said shaftmeans, a relatively rigid operating member joined to said shaft meansand extending generally away from the axis of said shaft means, and pushbutton means mounted for reciprocation substantially transverse of saidoperating member and engaging said operating member in a regionsubstantially spaced from said axis of said shaft means, said pushbutton means including a laterally projecting stop and said frame meansincluding a stop projecting into the path of reciprocation of said pushbutton means stop, one of said stops being annular in form and having atleast one face inclined with respect to a plane normal to the line ofreciprocation of said push button means, whereby upon rotation of saidpush button means about its line of reciprocation, the relative stoppingposition of said push button means with respect to said frame may beadjusted.

2. Mechanism in accordance with claim 1 including another stop on saidframe means, one of said frame means stops being positioned between saidoperating member and said push button means stop, and the other of saidframe means stops being positioned on the opposite side of said pushbutton means stop, whereby to provide limits for both the operated andunoperated positions of said push button means.

3. Snap-acting mechanism comprising frame means defining a pair ofspaced pivot bearing means, resilient leaf spring means compressed andbowed between said pivot bearing means, shaft means formed at at leastone end of said leaf spring means and journalled in the adjacentcorresponding pivot bearing means, said shaft means being formedintegral with said leaf spring means and having a looped bent-overconfiguration of the end of said leaf spring means, said bentover end ofsaid leaf spring means further having a serpentine configuration to forma return spring for said leaf spring means to return said leaf springmeans from an astable bowed position in said frame to a stable bowedposition therein, means for afiixing the extremity of said bent-over endof said leaf spring means to said frame means, and reciprocally movableactuating means mounted in said frame means for actuating said leafspring means from the stable bowed position in said frame to the astablebowed position therein.

4. Snap-acting mechanism comprising frame means defining a pair ofspaced pivot bearing means, resilient leaf spring means compressed andbowed between said pivot bearing means, shaft means formed at at leastone end of said leaf spring means and journalled in the adjacentcorresponding pivot bearing means, said shaft means being formedintegral with said leaf spring means and having a looped bent-overconfiguration of the end of said leaf spring means, said bent-over endof said leaf spring means further having a serpentine configuration toform a return spring for said leaf spring means to return said leafspring means from an astable bowed position in said frame means to astable bowed position in said frame means, means for affixing theextremity of said bent-over end of said leaf spring means to said framemeans, a rel atively rigid operating member mounted on said shaft meansand extending away from the axis of said shaft means, and reciprocallymovable push button actuating means mounted in said frame means forengaging said operating member so as to actuate said leaf spring meansfrom said stable bowed position to said astable bowed position.

5. The mechanism defined in claim 4 in which said reciprocally movablepush button actuating means is rotatable in said frame means andincludes a longitudinal protuberance at the end thereof adjacent saidoperating member, said protuberance being eccentric with respect to theaxis of rotation of said actuating means, so that rotation of saidactuating means in said frame means variably adjusts the distance fromthe axis of said shaft means of the engagement of said protuberance withsaid operating member.

6. The mechanism defined in claim 4, wherein said push button actuatingmeans includes a radially projecting annular stop member, and said framemeans includes a pair of space stop members for selective engagementwith said annular stop member respectively to limit the reciprocalmovement of said actuating means.

References Cited in the file of this patent UNITED STATES PATENTS2,515,324 Thomson July 18, 1950 (Sther references on following page)Fiske Mar. 18, 1958 Swanson July 8, 1958 FOREIGN PATENTS Australia Sept.1, 1938 Great Britain July 25, 1951

